Pitman arm



April 3o, 1940.

E. s. MaePHERsoN `PITMAN ARM Filed oct. 3, 1938 m m w w Patented Apr.30, 1940 UNITED STATES PATE `PITMAN ARM Earle S. MacPherson,

NT OFFICE Detroit, Mich., asslgnor to y General Motors Corporation,Detroit, Mich., a corporation of Delaware e vApplication October` 3,

2 Claims.

nism. l

apparent during theA course of the `following l specification havingreference to the accompanying drawing wherein Figure 1 is a planview ofa portion of an automobile showing the steering mechanism; Figure 2 isan enlarged detail view of the pitman arm structure with parts insection as on line `2---2 of Figure 1; Figure 3 shows the structure ofFigure 2 as viewed from the top, and Figure 4 is a detail section takenon line` 4--4 of Figure 2.

In the drawing the reference character I indicates` a steering columnassembly having the ual hand wheel at the upper end and the gear case 3l5 frame 4. Projecting downwardly from the gear case is the rockshaft 5on which is mounted the swinging pitman arm, which in the presentinstance may consist of a pair of forgings arranged side by side inoverlapping relation and D fastened one to the other as a unit assembly.At the free or swinging end of .the section "I are fastened a pair ofball studs 8-8 for joining to the pitman arm in end to end alignment apair i of tie rods 9 and I0 extending transversely of the vehicle `forconnection` at their outer ends withthe steering arms of the road wheelsII and I2, respectively. Any suitable suspension arrangement may beemployed for mounting the I- chassis frame on the road wheels, thatillustrated inthe drawing being of a well known independent wheelsuspension structure. It involves upper and lower arms I3 and I4,respectively, pivoted at their inner ends to the chassis frame and attheir outer ends to the steering wheel knuckle with at the lower endmounted on the chassisy 193s, serial No. (Cl. 74-559) a coil spring inI4 to the rockshaft terposed between the lower arm and the chassis frameI. Referring more be seen that the particularly to Figure 2 it will armsection vwhich is splined 5 is provided with a pair of bearings oropenings therethrough spaced radially of each other with respect to theaxis of the rockshaft 5. `These openings extend through the arm in adirection swinging arm oppositely taper ly from the each may comprise 10`central internal rib I5. Received thereby .are a pair of frusto-conicalor tapered plugs I 6 of rubber or other elastic deformable materialinserted from opposite sides of the openlng and tted to the internal ribI metal rings I1 openings through the plugs. rubber plugs positioned in5. Flanged the central Mounted in the are carried within each vided, onefor each of the openings in the arm section 6.

For convenience these rately from the arm and by projecting, throughopenings in the arm,

studs are formed sepaare later secured thereto end portion I9 of eachstud and riveting over the head is an annular spacer ange 2| stud andwhich jacent plug I6.

a reduced threaded portion 22 engaged by theL riveted head integral withthe also engages the end of the ad- At its opposite end the stud hasforming a shoulder 23 against which bears a clamping plate 24 fastenedon the stud 22 by the The shoulder tightening the nut nut 25. provides adenite limit for 25 so that by proper selection of parts andpredetermination of manufacturing tolerances the workman is relieved ofthe necessity of exercising care in assembling the parts.

In the assembly the plate 24 and the annular flange 2| exert an plugs I6causing endwise pressure on the rubber the internal deformation thereofto conform to the shape of 'the space in which they are received and theload on the rubber affords va tight co nnection. 'I'he pressure plate 24resist relative tions and at metal contact.

parts from each or spacers the t movement between the arm seco the sametime eliminate metal to Because of the insulation of the other throughthe rubber collars ransmission of shocks is reduced 5 v and road noisesand vibrations are cushioned by vide a channel the reaction in therubber.

As a further precaution against relative movement and to insure denitealignment of the arm sections the section i is formed along each sidewith a pair or spaced lugs -25, as seen particularly in Figure 3, andthese projecting arms in cooperation with each other and the arm Sproshaped pocket for 'the reception of the overlapping portion of thearm 'l4 thereby providing ,a positive limit to resist relativedisplacement of the sections comprising the pitman arm assembly.

I claim: t

1. A steering pitxnan comprising a pair of sections having adjacent endportions in overlapping relation, laterally spaced upstandingprojections on one of the sections forming a channel shaped pocket toreceive the overlapping portion of the l other section, one Y tionhaving a pair of radially spaced openings extending therethrough in adirection transverse to the plane of swinging movement of the pitinan,elastic bushings within said openings, anchor studs projecting from theother section through said bushings and having shouldered ends, aconnecting plate fitted to said ends for the application of endwisepressure on 5 the bushings and seated on the shoulders and meansretaining the plate 0n said studs.

2. In a two part steering pitman arm, a pair of pins fixed to one partand projected laterally therefrom through spaced openings in the otherw` part, said pins being formed at their free ends beyond said openingswithishouldered abutment seats, insulating spacers of elastic deformablematerial sleeved on the pins and tted to and contained within `saidopenings tor the transmis- 15 sion therethrough of motion between thepitman arm parts, a clamp plate tying the free ends of said pinstogether and exerting predetermined endwise pressure on the spacers, andmeans hold- Y ing the plate against said shouldered abutments. 20

mam s. mcrnnnson.

